Absorbent articles of the present kind generally comprise a liquid pervious coversheet (topsheet) that is located adjacent the wearer's body, a liquid impervious coversheet (backsheet) that is located distant from the wearer's body and adjacent the wearer's clothing and an absorbent layer interposed between the liquid pervious topsheet and the liquid impervious backsheet. Sometimes however, in specific absorbent articles, the absorbent layer can also be renounced to.
As liquid-permeable coversheets (topsheets), it is customary to use nonwovens and perforated film materials. Both are generally made from inherently hydrophobic, synthetic polymer materials such as polyethylene or polypropylene. To provide these materials with wettability and to enhance liquid permeability, they are typically treated with wetting agents (surfactants).
The treatment with wetting agents renders the inherently hydrophobic material hydrophilic. In some aspects, this treatment is not satisfying. First of all, care must be taken that the wetting agent is firmly bound to the topsheet surface since otherwise already the first insults of body fluid (urine) can wash off the wetting agent. Further, the binding of wetting agents to the topsheet surface also makes the topsheet surface prone to absorb moisture which may cause an unpleasant “wet feel” for the wearer of the absorbent article. Moreover, it would be desirable to provide a topsheet material that also exerts a certain barrier function against rewet from the absorbent core if the same has reached or exceeded its absorption capacity. Hydrophilic topsheet materials, however, are hardly capable of contributing to the fluid management after absorption.
An improved fluid management, superior surface dryness and/or lower rewet can be achieved by inserting fluid management layers, partially also referred to as “acquisition/distribution layers” between the topsheet and the absorbent core, optionally in combination with means for increasing the absorption capacity of the absorbent core, for instance the use of superabsorbent polymers (SAP). This is taught for instance by U.S. Pat. No. 5,558,655, EP 0 640 330 A1, EP 0 631 768 A1, WO 95/01147 or WO 00/35502. However, even the use of high performance liquid/acquisition distribution layers is not capable of overcoming the afore-mentioned disadvantages. To achieve a superior surface dryness it is also known from EP 1 003 454 A1 in the name of the present applicant to use liquid-permeable coversheets comprising one hydrophilic and one hydrophobic material layer. The first material layer is plasma- or corona-treated and has a hydrophilic surface and is situated far away from the wearer. The second material layer is made from an inherently hydrophobic material being in contact with the skin of the wearer, which means that this surface remains dry even after wetting. In this embodiment of EP 1 003 454 A1, the first material layer, that is the inner fiber structure functions as drainage material which has the ability to drain liquid from the upper (second) layer nearest the user.
In view of the above, it is one technical object of the present disclosure to provide an absorbent article with improved surface dryness.
It is one further technical object of the present disclosure to provide an absorbent article showing optimal hydrophilic/hydrophobic properties for achieving a good fluid management upon wetting.
It is one further technical object of the present disclosure to provide an absorbent article showing a barrier function against rewet from the absorbent body.
It is one further object of the present disclosure to achieve the above aims with as few material layers as possible.